Functions of Protein in Food

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Functions of Protein in Food
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The food scientist

• To determine how effectively proteins will work
  in a food product, scientists analyze three
  PHYSICAL CHARACTERISTICS
• 1. WATER ABSORPTION
• 2. SOLUBILITY
• 3. VISCOCITY (the ability to flow when poured)
• 1 and 3 can be altered by denaturization!

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1. Form Gels

• Ex. when you heat the protein gelatin in water
  then cool form gel (jello)
• Ex. when a mixture of eggs, milk, and sugar is
  heated form gel (custard)

• A gel is a mixture of mostly fluids locked in a
  tangled mass of denatured coagulated proteins.
  The liquid keeps the proteins from collapsing and
  the proteins keep the liquid from flowing away.

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Gelatin Mixtures

• Once rehydrated, a gelatin must be kept
  refrigerated
• Gels are weakened by acids, sugar, and fruit or
  vegetable pieces
• Other uses for gelatin
• to provide structure support
• to stabilize foam in whipped products
• to thicken puddings pies
• to control crystal growth in frozen foods

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2. Texturize

• ex. soy protein products are texturized by heat
  coagulation under pressure.
• ex. processed cheese is made by mixing melting
  together several natural cheeses. This heating
  process denatures the protein gives it a
  smoother texture.

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3. Emulsify

• An EMULSION is a stable mixture of a fat
  liquid.
• Emulsified products have 3 parts
• a non-polar substance, like fat
• a polar liquid, like water
• an emulsifier (a molecule with a polar
  non-polar end)
• Stable emulsions usually require heat or
  mechanical action to denature protein THEN form
  an emulsion
• Temporary emulsions can be created by shaking
  together a fat polar liquid without an
  emulsifier

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Emulsifiers

• Egg Yolk- used in ice cream, mayo, dressings

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Other food product emulsions kept together by
protein

• milk, cream, butter, cheese
• CASEIN present in milk serves as a protein
  emulsifier in these foods
• HOMOGENIZED milk is a stable emulsion- milk is
  forced through screens at high pressure,
  rupturing membranes around the fat globules, and
  reducing their size. This structure change makes
  the casein better able to bond to the fat.

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4. Form Foams

• Ex. meringue, foam cakes, marshmallows, whipped
  cream, whipped toppings, ice cream, soufflés,
  bread
• In a foam, gas is suspended in a liquid or
  semisolid.

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Three ways to make a foam

• 1. Bubbling gas through a mixture
• ex. blowing air through a straw into a glass of
  milk
• 2. Whipping or beating the protein mixture
• ex. meringue
• 3. A sudden release of pressure
• ex. aerosol cans of whipped cream

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5. Develop Gluten

• GLUTEN is a strongly cohesive elastic protein
• Its formed by mixing flour with liquid and then
  stirring or kneading.
• The gluten strands are stretched as CO² air
  become trapped between them during baking/cooking

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ATTENTION Gluten formation in progress

• Gluten is only found in wheat flours
• Dough made with other grains such as rye
  or corn must be mixed with wheat flour
• Other proteins can interfere w/ gluten
  development- mostly milk! This is why we use
  scalded milk products when baking (denatured milk
  protein)